1. Field of the Invention
The present invention relates to an optical disk device for recording or reproducing information onto/from an optical information recording medium such as an optical disk and in particular, to an optical disk device for recording/reproducing information onto/from an optical disk having a plurality of layers recordable or reproducible layers (hereinafter, simply referred to as recording/reproducing layer) and its tilt adjustment method.
2. Description of the Related Art
Generally, in an optical disk device for recording or reproducing information onto/from the recording/reproducing layer formed on the optical disk as an optical information recording medium, as shown in FIG. 12, a disk warp and clamping error cause inclination (so-called tilt value) of a disk with respect to the optical axis of the laser beam, which in turn generates coma aberration on the optical spot focused. This deteriorates the information recording or reproducing operation performance. For this, in order to reduce the deterioration of the recordability or readability caused by disk inclination (tilt value) with respect to the optical axis of the laser beam, it is necessary to perform tilt adjustment and tilt control by detecting and correcting the tilt amount.
On the other hand, recently, for example, a DVD which is one type of such an optical information recording medium, especially DVD-Video (DVD-ROM for recording and reproducing a movie is widely spread. Such a medium often has a two-layered recording/reproducing layer on one side (that is, has a plurality of recording/reproducing layers) as recording capacity of the video data increases. Inn this case also, in the same way as the aforementioned, it is necessary to provide means for correcting/controlling the tilt value optimally.
Conventionally, in an optical disk device for recording or reproducing information onto/from an optical disk having a plurality of recording/reproducing layers, there have been already suggested some techniques related to such a tilt adjustment and tilt control. For example, WO 00/079525 discloses a method for adjusting the tilt control means in a fine adjustment. That is, when recording or reproducing information onto/from an optical disk having a plurality of data layers, tilt control means is controlled on each of the plurality of data layers of the optical disk so as to set the tilt position (that is, an angle defined by the data layers of the optical disk and the optical axis of the laser beam) and furthermore, at the set tilt position, the tilt control means is adjusted according to the jitter detected.
Moreover, for example, JP-A-2003-30842 discloses a method for setting a recording condition (recording waveform parameter) appropriate for an optical disk having a plurality of recording layers, wherein data trial write is performed on the recording layers starting at the farthest recording layer from the optical beam incident surface and the data written by trial is read so as to set the recording waveform parameter including the tilt position (value).